Colitis is characterized by colonic inflammation and impaired gut health. Both features aggravate obesity and insulin resistance. Host defense peptides (HDPs) are key regulators of gut homeostasis and generally malfunctioning in above-mentioned conditions. We aimed here to improve bowel function in diet-induced obesity and chemically induced colitis through daily oral administration of lysozyme, a well-characterized HDP, derived from Acremonium alcalophilum . C57BL6/J mice were fed either low-fat reference diet or HFD ± daily gavage of lysozyme for 12 weeks, followed by metabolic assessment and evaluation of colonic microbiota encroachment. To further evaluate the efficacy of intestinal inflammation, we next supplemented chow-fed BALB/c mice with lysozyme during Dextran Sulfate Sodium (DSS)-induced colitis in either conventional or microbiota-depleted mice. We assessed longitudinal microbiome alterations by 16S amplicon sequencing in both models. Lysozyme dose-dependently alleviated intestinal inflammation in DSS-challenged mice and further protected against HFD-induced microbiota encroachment and fasting hyperinsulinemia. Observed improvements of intestinal health relied on a complex gut flora, with the observation that microbiota depletion abrogated lysozyme’s capacity to mitigate DSS-induced colitis. Akkermansia muciniphila associated with impaired gut health in both models, a trajectory that was mitigated by lysozyme administration. In agreement with this notion, PICRUSt2 analysis revealed specific pathways consistently affected by lysozyme administration, independent of vivarium, disease model and mouse strain. Taking together, lysozyme leveraged the gut microbiota to curb DSS-induced inflammation, alleviated HFD-induced gastrointestinal disturbances and lowered fasting insulin levels in obese mice. Collectively, these data present A. alcalophilum- derived lysozyme as a promising candidate to enhance gut health.

Background & Aims: To enable rapid proliferation, colorectal tumor cells up-regulate epidermal growth factor receptor (EGFR) signaling and perform high level of aerobic glycolysis, resulting in substantial lactate release into the tumor microenvironment and impaired anti-tumor immune responses. We hypothesized that an optimized nutritional intervention designed to reduce aerobic glycolysis of tumor cells may boost EGFR-directed antibody (Ab)-based therapy of pre-existing colitis-driven colorectal carcinoma (CRC). Methods: CRC development was induced by azoxymethane (AOM) and dextran sodium sulfate (DSS) administration to C57BL/6 mice. AOM/DSS treated mice were fed a glucose-free, high-protein diet (GFHPD) or an isoenergetic control diet (CD) in the presence or absence of i.p. injection of PBS, an irrelevant control mIgG2a or an anti-EGFR mIgG2a. Ex vivo, health status, tumor load, metabolism, colonic epithelial cell differentiation and immune cell infiltration were studied. Functional validation was performed in murine and human CRC cell lines MC-38 or HT29-MTX. Results: AOM/DSS treated mice on GFHPD displayed reduced systemic glycolysis, resulting in improved tumoral energy homeostasis and diminished tumor load. Comparable but not additive to an anti-EGFR-Ab therapy, GFHPD was accompanied by enhanced tumoral differentiation and decreased colonic PD-L1 and splenic PD-1 immune checkpoint expression, presumably promoting intestinal barrier function and improved anti-tumor immune responses. In vitro, glucose-free, high-amino acid culture conditions reduced proliferation but improved differentiation of CRC cells in combination with down-regulation of PD-L1 expression. Conclusion: We here found GFHPD to metabolically reprogram colorectal tumors towards balanced OXPHOS, thereby improving anti-tumor T-cell responses and reducing CRC progression with a similar efficacy as EGFR-directed antibody therapy.

Objective: The AT1 receptor blocker Telmisartan (TEL) is beneficial for the treatment of individuals suffering the Metabolic Syndrome as TEL reveals not only antihypertensive effects but also improves the glucose and lipid control and lowers body weight. As we have recently shown that TEL has impact on gut microbiota and brain barrier function we here investigated whether TEL influences gut barrier function which may participate in decrease of energy intake. Design and method: BL6 mice were fed with chow or high fat diet (45% fat) and were additionally treated with vehicle (CONchow or CONHFD) or TEL (8 mg/kg/d, 12 w, TELchow or TELHFD). Visceral and subcutaneous fat mass was quantified by MRI. Segments of large intestine were Canoy fixed to determine thickness of mucus by immunohistochemistry. PAS staining was performed for depicting goblet cells. The signalling pathway being involved in necroptosis was investigated by Western blots and qPCR. Results: Compared to chow feeding, gain in body weight increased by HFD (3.4±0.5 vs. 14.4g±1.2 g) and was reduced by TEL (1.7±0.5 vs. 2.8±0.5g). Visceral fat and liver mass was higher in CONHFD than CONchow but remained normal by TEL treatment. The mucus thickness was lower in CONHFD than CONchow. Independent on feeding, TEL additionally reduced mucus thickness. Numbers of goblet cells were not affected by HFD feeding and TEL treatment. RIP3 was particularly increased in TELHFD mice, while muc2 and ki67 almost remained unaffected by TEL. Conclusions: In contrast to our expectation, the antiobese effect of TEL was associated with a decrease in mucus thickness. Increase in RIP3 indicates that necroptosis may be enhanced by TEL. Further studies have to be performed to elucidate whether this detrimental TEL effect is true and be relevant for gastrointestinal function.